a1 Department of Physics, New York University, 4 Washington Place, New York, NY 10003, USA
a2 Department of Mathematics, Harvey Mudd College, 301 Platt Boulevard, Claremont, CA 91711, USA
a3 Applied Mathematics Laboratory, Courant Institute, New York University, 251 Mercer Street, New York, NY 10012, USA
We investigate the dynamics of rigid bodies (hollow ‘pyramids’) placed within a background airflow, oscillating with zero mean. The asymmetry of the body introduces a net upward force. We find that when the amplitude of the airflow is above a threshold, the net lift exceeds the weight and the object starts to hover. Our results show that the objects hover at far smaller air amplitudes than would be required by a quasi-steady theory, although this theory accounts qualitatively for the behaviour of the system as the body mass becomes small.
(Received September 09 2009)
(Revised January 27 2010)
(Accepted January 30 2010)
(Online publication March 19 2010)